Effect of temperature on the inhibition of the GABA-gated response by intracellular calcium.
The effects of the voltage-dependent Ca2+ inward current (ICa) on gamma-aminobutyric acid (GABA)-induced Cl- current (ICl) in isolated frog sensory neurons were examined at different temperatures and with different concentrations of external Ca2+ using the 'concentration-clamp' technique. The total amount of inhibition of GABA-induced ICl by a preceding ICa increased in a hyperbolic manner with increasing Ca2+ influx. The time course of recovery of the GABA response after inhibition by Ca2+ influx followed a single exponential and was facilitated by warming but slowed dramatically by a slight cooling from 20 to 15 degrees C in spite of a decrease in Ca2+ influx. It is discussed that the energy-dependent, temperature-sensitive ionic pump and exchange systems at the surface membrane and intracellular organelles regulate the cytoplasmic free Ca2+, thus explaining the quantitative effects of Ca2+ influx and temperature on the inhibition of the GABA-gated Cl- channel.
Maruyama
T
T
Department of Neurophysiology, Tohoku University School of Medicine, Sendai, Japan.
Ikemoto
Y
Y
Akaike
N
N
D000818:Animals; D002118:Calcium / Q000502:physiology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009433:Neural Inhibition / Q000187:drug effects; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology*; D011892:Rana catesbeiana; D013696:Temperature; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology / Q000502:physiology*
D005680:gamma-Aminobutyric Acid; D002118:Calcium